Scleral lenses have been used to restore sight to those with injured or diseased corneas and to relieve discomfort from dry eye disorders. The incidence of dry eyes in the general population is estimated to be 15%, of which nearly 2 in 10 have symptoms severe enough to significantly impact their quality of life. Globally, this corresponds to 3% of the worldwide population and approximately 9,240,000 severe dry eye patients in the United States alone.
In addition, there are millions of people whose eyes are not normally dry but feel dry after wearing conventional contact lenses for an extended period of time.
A scleral lens is a large contact lens that rests on the white scleral region of the eye and is vaulted over the cornea as shown in FIG. 1. The gap 103 between the back-interior surface of the lens and cornea is typically filled with saline solution which acts like a liquid bandage to soothe the thousands of nerves on the corneal surface. In some applications, medication can be added to, or replace, the saline solution to assist with healing an injured eye.
To ensure that the lens does not irritate the nerves on the scleral surface, the shape of the bearing surface 100, shown in FIG. 1, must match the unique three-dimensional shape of the patient's sclera, including the regions normally covered by the eyelids.
Unfortunately, there is currently no way to precisely measure scleral shape. As a result, to find a comfortable fitting lens, scleral lenses are manually selected from a set of up to 2000 trial lenses to find a suitable fit to the patient's scleral surface. This is an iterative, expensive, and time-consuming process which can take several weeks. If a close-fitting trial lens can be found, frequently it must be further modified to optimize fit.
If the patient has an abnormally shaped eye, due to an injury or disease for example, as shown in FIGS. 2a, 2b, 2c, 2d, fitting may not be possible because there is no trial lens that conforms to the shape of the irregular shaped bearing surface.
There is also a category of smaller diameter scleral lenses whose bearing surface lies on both sides of the limbus straddling the sclera and outermost regions of the cornea. For injured eyes, these lenses may be even more difficult to fit because they must conform to injuries in both the corneal and scleral regions of the bearing surface, as shown in FIGS. 2c and 2d. 
Assuming a well-fitting trial lens can be found, the next step in the prior art approach is to determine the optical properties of the vaulted optics that needs to lie in front of the patient's cornea to properly focus light onto the retina.
It is important to emphasize that while a trial lens has no patient-specific vision correction optics, it must be placed on the patient's eye and worn to enable design of the optics because the fluid (typically saline) that lies between the back surface of the scleral lens and front surface of the cornea; alters how light rays are bent at both the fluid-cornea and fluid-back-scleral-lens boundaries.
With the trial lens now in place, the doctor or eye care practitioner performs an optical refraction (i.e. places different known lenses in front of the trial scleral lens) to determine the optical power of the scleral lens optics.
Once the refraction is completed, then knowing the required optical power and the bearing surface shape of the best fitting trial lens, a patient specific custom scleral lens can now be manufactured.
A prior art attempt to measure scleral shape without iteratively interchanging trial lenses is described by Gemoules, U.S. Pat. No. 7,862,176 B2 entitled “Method of Fitting Rigid Gas-permeable Contact Lenses from High Resolution Imaging”. Gemoules' fitting method is based on using a digital acquisition device to acquire a two-dimensional cross sectional sagittal image of the eye which includes the sclera, as shown in FIG. 3a. However, the eye is not two dimensional in shape, it is three-dimensional, as shown in FIGS. 5a, 5b and 5c, so a cross sectional image is a poor approximation to a three-dimensional shape. This limitation is further illustrated by the injured eye shown in FIG. 3b. FIG. 3b shows multiple independent meridians in a quadrant over an injured region to enable the back-lens surface to better conform to eye surface topology. Each radial meridian can have different independent spatial Z height values. The cross-sectional sagittal image shown in FIG. 3a could easily correspond to a scan taken across line 301-307 in FIG. 3b, which does not reveal the presence of the injury shown by scan lines 302, 303,304, and 305, such scan lines also referred to as meridians. In addition, and while not addressed by Gemoules, attempts to approximate the three-dimensional shape by acquiring multiple independent two-dimensional scans around the eye has failed in the past because the spatial position of the eye moves between scans.
Svochak, U.S. Pat. No. 7,296,890 B2 entitled “Contact Lens with Controlled Shape,” presents means for creating a contact lens that sits on the cornea and whose back-surface shape is defined by four (4) base curves, effectively one curve per quadrant. This technique for designing a scleral lens bearing surface has multiple limitations. First, it cannot conform to small injuries, protrusions or irregular shapes within a region of a generally different shape, as shown in FIGS. 2a, 2b, 2c, and 2d herein. Second, the base curve of the cornea is almost always different from that of the sclera with the demarcation point being the limbus. A scleral lens that straddles both regions must conform to this complex change in curvature across the region boundaries (as illustrated in FIG. 10 at arrow 1003) and Svochak is only concerned with lenses conforming to the cornea. Third, the four-base-curve solution cannot follow all possible three-dimensional topology changes in an eye. If an eye or optimized well-fitting lens requires more than 4 base curves to define its shape, as for the injured eyes in FIGS. 2a-d, Svochak's method is not applicable.
Sindt, U.S. Pat. No. 9,551,885 B2 entitled “Prosthetic Lenses and Methods of Making the Same” describes methods of applying a foreign material to the surface of an eye to obtain a physical impression thereof. The impression is then used to determine the back surface of a lens. This procedure is highly invasive and may not be well tolerated by patients with sensitive eyes.